Fine automotive finishing and artistic paint finishing such as commonly applied on the sides of some automobiles or vans, requires a coordination of different colors, shades or layers of paint to give the desired end finish. For example, three different coats of paint often are applied to an automobile. A base coat and then a microflake coat typically are applied to the automobile, followed by a protective coating of clear, automotive finish. Typically, between each different paint coat, a new spray gun adapted for use with a different paint must be prepared or the liquid-holding canister, i.e. cup as commonly referred, is removed from the spray head unit and a new canister which contains a different paint therein, secured to the unit. The use of a different compressed air spray gun for each color or coating is cost prohibitive. Changing the canister on a single spray head unit for each color or coating could be less expensive. However, this is time consuming and can become bothersome to an operator.
Some compressed air spray guns, such as found in U.S. Pat. Nos. 1,863,782 to Young; 1,948,401 to Smith et al; and 3,135,467 to Greenman, incorporate different attachments which provide for multiple canister use on a single spray head unit. Although these devices do provide an enhanced paint spraying operation by eliminating the need for using two or more air spray guns or repeatedly changing cups between coats, there is an apparent limitation in their use. Cleaning of each device is difficult after use. Both Smith and Young have integral branch pipes or tubes which are difficult to clean and can clog easily. Additionally, the housing or cover securing the multiple canisters lessens the efficiency of the spray gun operation because the vacuum draw in the integrally connected branch pipes or tubes is lessened. Also, the complexity in the design of these devices makes their manufacturing more difficult and their designs do not readily accommodate the use of conventional paint canisters.
The device disclosed in Greenman does not suffer from a vacuum loss because it uses a positive pressure system where each canister is pressurized and the liquid contained is forced under pressure into the spray head unit. The amount of liquid or paint flowing from each canister into the spray head unit can be regulated so that various shades or hues can be produced by mixing various colors of paint during spray. This device also has apparent limitations. Because the canisters are pressurized, additional air pipes and air pressure chambers are required in the main structure to induce pressure to the paint canisters. Additionally, this device discloses a complex valve unit controlling the flow of paint from each canister. Each valve unit includes at least a valve pin, compression spring, valve pin guide and washers. Not only do the large number of parts and complexity of the design increase manufacturing costs, but also cleaning of the apparatus is made more difficult because a larger number of parts, such as in the valve unit, must be disassembled from the main structure and then reassembled.
It is therefore a primary object of this invention to provide a compressed air spray gun adapted for multi-canister use and which includes a mounting block for securing thereto conventional liquid-holding canisters and a spray head unit such as commonly used in the industry and which provides selective and individual regulation of fluid flow from the canisters into the spray head unit.
It is another object of this invention to provide a compressed air spray gun adapted for multi-canister use and which includes a mounting block for securing thereto conventional liquid-holding canisters and a spray head unit such as commonly used in the industry and which is simple in design to facilitate cleaning and reduce manufacturing costs and which provides selective and individual regulation of fluid flow from the canisters into the spray head unit.
It is another object of this invention to provide a compressed air spray gun adapted for multi-canister use and which includes a mounting block for securing thereto conventional liquid-holding canisters and a spray head unit such as commonly used in the industry and which provides selective and individual regulation of fluid flow from the canisters into the spray head unit by valve means which is simple in design and includes few parts.